Currently, there are three kinds of contact-type bearings that are most commonly being adopted by conventional compressors, which are the ball bearing, the roller bearing and the sliding bearing. However, as such mechanically sealed contact-type bearings can not operate without suffering contact abrasion and they should required to be cooled down by flowing oils during operation, problems such as shaft power wastage and oil vapor pollution are inevitable that are usually the reasons causing those conventional compressors with the aforesaid contact-type bearings to operate at low efficiency.
For avoiding the aforesaid problems, there are magnetic bearings and gas bearings that are already available for the compressors. However, those two types of bearings are still has shortcomings. For the magnetic bearings, they are not popular since they can be very costly to manufacture, not to mention that their ability to support a load are restricted by the magnetic saturation of the bearing's material. For the gas bearings, the compressibility of the gases used in such gas bearing will cause the gas bearings to become unstable.
Moreover, there is a prior-art magnetic-gas bearing being provided in CN 200510041540.5, which can prevent the baring to contact directly with its corresponding shaft by the use of a pneumatic device. However, the load performance of such prior-art magnetic-gas bearing is still not satisfactory and is hard to improve. In addition, as the magnetic poles in such prior-art magnetic-gas bearing are radially arranged while having its complaint foils to be fitted in the gaps formed between the magnetic poles and its corresponding shaft, the penetration of the magnetic lines of those magnetic poles are adversely affected and thus lower the magnetic levitation of the bearing.